JP3415377B2 - Manufacturing method of high magnetic flux density grain-oriented electrical steel sheet with extremely low iron loss - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention proposes a method for producing a grain-oriented electrical steel sheet having a particularly high magnetic flux density and a very low iron loss among the grain-oriented electrical steel sheets used for the cores of transformers and generators. It is a thing.

It contains Si and has a crystal orientation of (110)
Since the grain-oriented electrical steel sheet oriented in the [001] orientation or the (100) [001] orientation has excellent soft magnetic properties, it is widely used as various iron core materials in the commercial frequency range. On the other hand, the characteristic required for magnetic steel sheets is generally the loss when magnetized to 1.7 T at a frequency of 50 Hz.
It is important that the iron loss represented by W _17/50 is low. The iron loss of the iron core as a generator or a transformer can be significantly reduced by using a material with a low W _17/50 value, so the development of a material with a low W _17/50 is strongly required year by year. Is coming .

[0003]

2. Description of the Related Art Generally, in order to reduce iron loss of a material, a method of increasing Si content effective for reducing eddy current loss to increase electric resistance, a method of reducing a steel plate thickness, a crystal grain A method of reducing the diameter and a method of increasing the degree of integration of crystal orientation to improve the magnetic flux density are known. Among these, we examined the method of increasing the Si content, the method of reducing the steel plate thickness and the method of reducing the crystal grain size. There is an undesired limit because it deteriorates workability and workability, and there is a limit naturally because the method of reducing the steel plate thickness causes an extreme increase in manufacturing cost.

Many of the above-mentioned methods for improving the magnetic flux density have been studied so far, and for example, Japanese Patent Publication No. 46-23820 (Heat treatment method for high magnetic flux density magnetic steel sheet) discloses that After adding Al and hot rolling 10
Proposed is a technology for applying high pressure under which the reduction ratio in the final cold rolling is 80-95% by precipitating fine AlN by annealing the hot-rolled sheet in the temperature range of 00-1200 ℃ and high temperature and then quenching. It is disclosed, and as a result, an extremely high magnetic flux density of 1.95 T at B ₁₀ is obtained. This is AlN finely dispersed and precipitated.
Has a strong action as an inhibitor that suppresses the growth of primary recrystallized grains, and by secondary recrystallizing only the nuclei having an excellent crystallographic orientation, it is intended to obtain a product having an excellent crystallographic structure. It is what

However, in this technique, the crystal grains are generally coarsened, and it is difficult to obtain a low iron loss.
In addition, since it is difficult to form a solid solution of AlN in the hot-rolled sheet annealing, it is difficult to stably obtain a product having a high magnetic flux density.

Separately from this, Japanese Patent Publication No. 58-43445 (method for producing cubic ridge oriented silicon steel) describes 0.0006-
A technique has been disclosed in which a magnetic flux density of 1.89T is obtained with B ₈ by using a steel containing 0.0080% B and 0.0100% or less N and devising decarburization annealing. This method was not industrialized because the magnetic flux density is low and the iron loss is not so good, but the product obtained by this method shows relatively stable magnetic properties, so it is an industrially preferable technique. is there.

[0007]

SUMMARY OF THE INVENTION The present invention uses B and N described above as inhibitor components to increase the degree of integration of crystal orientation to obtain a high magnetic flux density, and to prevent the coarsening of crystal grains and the deterioration of iron loss characteristics. It is an object of the present invention to propose a method of manufacturing a grain-oriented electrical steel sheet that can be eliminated.

That is, when the degree of integration of crystal orientations is increased, the crystal grains inevitably become coarse, leading to deterioration and instability of iron loss, and conversely, if the crystal grains are made finer, the degree of integration of crystal orientations is increased. Deteriorates and the magnetic flux density decreases. Due to such an antinomy state, it has been impossible in the past to stably manufacture a low iron loss material with an extremely high magnetic flux density. Therefore, in the present invention, in the method for producing a grain-oriented electrical steel sheet using BN as an inhibitor, the magnetic flux density B ₈ is extremely high, and the instability such as the coarsening of the crystal grains of the inherent product is solved. is there.

[0009]

The present invention focuses on the precipitation and dispersion state of BN, which is an inhibitor, in order to eliminate such a trade-off condition, and by adopting a precipitation method completely different from the conventional one, it is possible to obtain extremely fine particles. It was found that it is possible to obtain a strong suppressing effect on the growth of primary recrystallized grains by precipitating BN in the above, and it was achieved by effectively utilizing this. That is, the gist of the present invention is as follows.

1. C: 0.025-0.095 wt%, Si: 1.5-
Contains 7.0 wt%, Mn: 0.03 to 2.5 wt% and the sum of one or two of S and Se: 0.003 to 0.040 wt%
And the balance being the material a steel slab comprising the composition of Fe and unavoidable impurities, the slab is heated to a temperature above 1350 ° C., after hot rolling, after subjected to hot rolled sheet annealing, between one cold after more final cold-rolled sheet thickness in <br/> rolling, subjected to primary recrystallization annealing to produce a grain-oriented electrical steel sheet by a series of steps of applying a final finish annealing after coating the subsequent annealing separator In this regard, B:
Including 0.0008 to 0.0085 wt% and N: 0.0030 to 0.0100 wt%, the finish rolling reduction of hot rolling is 85 to 99%
And the finish rolling end temperature in the range of 950 to 1150 ° C and the relationship between the Si content and B content of the material
After performing hot rolling within the range satisfying (1), 20 ℃ / s
Rapidly cool at the above cooling rate and wind it into a coil at a temperature of 670 ° C or less, and heat-rolled sheet annealing to a temperature of 800 ° C at 5-25 ° C
/ heated at a heating rate in the range of s, be performed under conditions in which less 150 seconds holding time in the temperature range of 900 to 1150 ° C., the cold rolling, reduction ratio by rolling a single cold: 80 ~ 95% in order to obtain the final cold rolled sheet thickness, and in the final finish annealing, during the temperature increase of at least 900 ° C or higher, the temperature is raised in the atmosphere containing H ₂ in this order. A method of manufacturing a high magnetic flux density grain-oriented electrical steel sheet having extremely low iron loss. [Note] 745 + 35X + 3Y ≦ T ≦ 900 + 35X + 3Y --- (1) However, T: finish rolling end temperature (° C) X: Si (wt%) Y: B (wtppm) 2. C: 0.025 to 0.095 wt%, Si: 1.5 to 7.0 wt%, M
n: 0.03 to 2.5 wt% and one of S or Se
Or a total of two kinds: 0.003 to 0.040 wt% is contained, and the balance is
Using a steel slab with a composition of Fe and unavoidable impurities
Then, the slab is heated to a temperature of 1350 ° C or higher and hot rolled.
Then, the hot-rolled sheet is annealed and then cooled twice with the intermediate annealing.
After final cold-rolled sheet thickness by hot rolling, primary recrystallization annealing
And then apply an annealing separator before final finishing firing.
For manufacturing grain-oriented electrical steel sheets by a series of blunting processes
Therefore, as an inhibitor component to the ingredient composition of the material,
B: 0.0008 to 0.0085 wt% and N: 0.0030 to 0.0100 wt%
The final rolling reduction rate of hot rolling is 85 to
99% range and finish rolling end temperature of 950 ~ 1150 ℃
Within the range and from the relationship between the Si content and B content of the material, the following
After hot rolling within the range that satisfies formula (1), 20 ℃
Quench at a cooling rate of / s or more and coil at a temperature of 670 ° C or less
Winding, hot-rolled sheet annealing and intermediate annealing,
The temperature is raised to 00 ° C at a heating rate in the range of 5 to 25 ° C / s,
Keep the holding time for 150 seconds or less in the temperature range of 900 to 1150 ° C.
It is done in that condition, the cold rolling, the first rolling
Rolling reduction: within the range of 15 to 60% and then after the intermediate annealing
The second cold rolling is performed in the rolling reduction range of 80 to 95% and finally cold rolled.
The thickness of the plate should be kept at least during the temperature rise during final finishing annealing.
Temperature above 900 ° C in an atmosphere containing H ₂
Extremely characterized by being sequentially combined with warming
Of high magnetic flux density grain oriented electrical steel sheet with low iron loss. [Note] 745 + 35X + 3Y ≦ T ≦ 900 + 35X + 3Y --- (1) However, T: finish rolling end temperature (° C) X: Si (wt%) Y: B (wtppm) 3. C: 0.025 to 0.095 wt%, Si: 1.5 to 7.0 wt%, M
n: 0.03 to 2.5 wt% and one of S or Se
Or a total of two kinds: 0.003 to 0.040 wt% is contained, and the balance is
Using a steel slab with a composition of Fe and unavoidable impurities
Then, the slab is heated to a temperature of 1350 ° C or higher and hot rolled.
After that, the final cold-rolled sheet thickness is obtained by cold rolling twice with intermediate annealing.
After that, primary recrystallization annealing was performed, and then annealing separator
After a series of steps of applying final finishing annealing after applying
When manufacturing grain-oriented electrical steel sheets ,
As an inhibitor component, B: 0.0008 to 0.0085 wt% and
And N: 0.0030 to 0.0100 wt%, hot rolling
Finish rolling reduction of 85-99%
Finish temperature in the range of 950 to 1150 ℃ and Si content of the material
From the relationship with the B content, heat within the range that satisfies the following formula (1)
After performing hot rolling, quenching at a cooling rate of 20 ° C / s or more
Winding the coil at a temperature of 670 ℃ or less, intermediate annealing,
Temperature up to 800 ℃ at a heating rate in the range of 5 to 25 ℃ / s
The holding time is 150 seconds or less in the temperature range of 900 to 1150 ° C.
In the cold rolling, the first time
Rolling is performed in the range of 15 to 60% in rolling reduction and then after intermediate annealing.
The second rolling is performed in the rolling reduction range of 80-95%
Use a cold-rolled sheet thickness and reduce the temperature during the final finishing annealing.
In an atmosphere containing H ₂ from a temperature of at least 900 ° C or higher
It is characterized in that it becomes a sequential combination with raising the temperature by
Manufacturing method of high magnetic flux density grain-oriented electrical steel sheet with extremely low iron loss
Law. [Symbol] 745 + 35X + 3Y ≦ T ≦ 900 + 35X + 3Y --- (1) provided that T: finish rolling end temperature (℃) X: Si (wt %) Y: B (wtppm) 4. The steel slab is further composed of Sb, Sn, Bi, Te, Ge, P, P
One or more selected from b, Zn, In and Cr
The composition above contains 0.0010 to 0.30 wt% respectively
The electrode according to any one of the above 1 to 3, characterized in that
Process for producing a high magnetic flux density oriented electrical steel sheet with low Umate iron loss.

5. The high magnetic flux density grain-oriented electrical steel sheet with extremely low iron loss according to any one of 1 to 4 above , wherein cooling in hot-rolled sheet annealing or intermediate annealing immediately before final cold rolling is performed at a faster cooling rate than natural cooling. Manufacturing method.

[0012] 6. High magnetic flux density directionality with extremely low iron loss according to any one of 1 to 5 above , wherein 0.005 to 0.025 wt% of decarburization is performed by hot-rolled sheet annealing or intermediate annealing immediately before final cold rolling. Manufacturing method of electrical steel sheet.

7. The final cold rolling is either hot rolling in the temperature range of 90 to 350 ° C or 100 to 300 ° C.
7. The method for producing a high magnetic flux density grain-oriented electrical steel sheet with extremely low iron loss according to any one of 1 to 6 above, which is an aging treatment between passes in a time range of 10 to 60 minutes.

Here, the treatment in the above 5 is a treatment to be carried out in order to bring the state of the amount of C dissolved in the solid solution by high temperature annealing into a supersaturated state, and to obtain a gas and / or gas so that the cooling rate becomes faster than the natural cooling. This is a process of spraying a liquid onto the steel sheet as a cooling medium. By this treatment, in addition to the effect of increasing the solid solution C, the effect of precipitating fine carbides in combination with the low temperature holding treatment during cooling can be obtained, and the magnetic characteristics can be further improved.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION First, the background of achieving the present invention will be described below based on experimental examples. Experiment 1 C: 0.08 wt% (hereinafter simply expressed as%), Si: 3.36%,
Mn: 0.07%, Al: 0.009%, Se: 0.018%, Sb: 0.025
%, B: 0.0020% and N: 0.008%, and the balance consisting essentially of Fe, 250 mm slabs for grain-oriented electrical steel, each of which is heated to a temperature of 1390 ° C. After finishing the rough rolling to a plate thickness of 45 mm at a temperature and finishing rolling to a plate thickness of 2.2 mm at a temperature of 1020 ° C, spray a large amount of cooling water to cool at a cooling rate of 50 ° C / s. Winding up the coil (coil A) at a temperature of 550 ° C, finishing the rough rolling of the other at a temperature of 1200 ° C to a plate thickness of 45 mm, and then finishing rolling at a temperature of 935 ° C to a plate thickness of 2.2 mm. After that, spray a normal amount of cooling water and cool it at a cooling rate of 25 ° C / s to 550
It was wound into a coil at a temperature of ° C (coil B).

These two kinds of hot-rolled plate coils A and B are divided into two (A-1, A-2 and B-1, B-, respectively).
2), A-1 and B-1 hot rolled sheet coils have a heating rate:
Hot-rolled sheet annealing is performed by heating up to a temperature of 1100 ° C at 12 ° C / s and holding for 30 seconds. The hot-rolled sheet coils of A-2 and B-2 have a heating rate of 12 ° C / s of 1170 ° C. After the temperature was raised to the temperature, the hot rolled sheet was annealed for 30 seconds.

These annealed sheets were pickled, cold-rolled at a temperature of 120 ° C. to a final cold-rolled sheet thickness of 0.27 mm, and then degreased at 850 ° C. for 2 minutes for decarburization. Subsequent recrystallization annealing was performed, an annealing separator containing MgO as a main component was applied to the surface of the steel sheet, and each was coiled.

Then, as the final finishing annealing condition, 800
The temperature is raised to a temperature of ℃ in the N ₂ atmosphere at a temperature rising rate of 30 ℃ / h, the temperature in the temperature range of 800 ~ 1050 ℃ N ₂ : 25%,
H ₂ : 10% at a heating rate of 15 ° C / s in a mixed atmosphere of 75%
Increase the temperature in the temperature range of 50 to 1200 ℃ and soak for 5 hours at 1200 ℃ in H ₂ atmosphere, and set the temperature increase rate in the temperature range of 1050 to 1200 ℃ to 20 ℃ / s. Up to the temperature of H
A heat cycle and atmosphere were adopted in which forced cooling was performed in _two atmospheres, and a temperature of 800 ° C. or less was cooled in an N ₂ atmosphere.

After the final finish annealing, the unreacted annealing separating agent was removed, and then a tension coat consisting of 50% colloidal silica and magnesium phosphate was applied to obtain each product.

Epstein-sized test pieces with the long side in the rolling direction were cut out from the respective products thus obtained along the direction perpendicular to the rolling direction, subjected to strain relief annealing at a temperature of 800 ° C. for 3 hours, and then subjected to a magnetic flux of 1.7 T. The iron loss W _17/50 and the magnetic flux density B ₈ at the respective densities were measured, and these steel sheets were macro-etched to investigate the average crystal grain size.
The results of these investigations are summarized in Table 1.

[0021]

[Table 1]

As is clear from Table 1, the product of the coil symbol A-1 having a high hot rolling finish temperature and a low hot-rolled sheet annealing temperature is compared with the product of the coil symbol B-2 which is a conventional condition,
Extremely high magnetic flux density (B ₈ ) and extremely low iron loss (
W _17/50 ) has been obtained. As a result of investigating the reason for obtaining such favorable results, the following has been found.

That is, in the conventional hot rolling, it was extremely difficult to uniformly and finely precipitate BN as an inhibitor, and the inhibitory power of BN as an inhibitor could not be sufficiently exhibited. In the coil symbol A-1 which has obtained good results in the above experiment, precipitation of BN in the hot rolling is suppressed as much as possible, and extremely fine BN is generated in the temperature rising process of the hot rolled sheet annealing in the subsequent cold rolling process. It was found to be precipitated, which brought about a strong inhibitory effect of the inhibitor.

When the process of fine precipitation of BN in the temperature rising process of this hot-rolled sheet annealing was investigated in detail, a large number of ultrafine precipitates were already present in the hot-rolled sheet and these were found to be B.
It was found to be the nucleus of N precipitation. This ultrafine precipitate is composed of sulfides such as MnS and CuS, selenides such as MnSe and CuSe, and composite precipitates thereof, and can be extremely finely precipitated in a range where the hot finish rolling temperature is appropriate. all right. That is, it has been found that the precipitation of BN should be suppressed in a state where defects such as dislocations due to processing exist in the steel at a high density. Here, hot finish rolling is
When the temperature is higher than the proper temperature, the density of defects existing in the steel decreases, and a sufficiently high precipitation density cannot be obtained. On the contrary, when the temperature is lower than the proper temperature, the precipitation becomes insufficient and both the ultrafine precipitations occur. The precipitation density of the part decreases. Further, since these precipitates are ultrafine, a small amount of 0.003 wt% or more is sufficient, but it is necessary to contain S and / or Se in the steel.

The point to be noted in this technique is the first
That is, the annealing temperature of the hot-rolled sheet is set to a low temperature so that re-dissolution of the BN precipitated in Step 1 and Ostwald growth do not occur. The lower limit of the appropriate annealing temperature in the present invention, since this annealing is intended to optimize the size of the crystal structure after annealing, if the annealing temperature is excessively low, recrystallization after rolling In the structure, the strength of the (110) grain, which is the nucleus of the secondary recrystallization, is insufficient, and the secondary recrystallization structure with a good orientation cannot be obtained. Therefore, in order to obtain sufficient strength of (110) grains, it is necessary to coarsen the crystal structure after annealing to a certain size or more. For this purpose, it is essential to raise the temperature to 900 ° C or more. . On the other hand, the upper limit of the hot-rolled sheet annealing temperature is the most important point to prevent re-dissolution of BN finely precipitated and Ostwald growth during the temperature rising process as described above. For this, 1150 ℃
It is necessary to anneal at the temperature below and for a soaking time of 150 seconds or less.

The precipitation phenomenon of BN at the time of heating the temperature of the hot-rolled sheet finishes up to a temperature of about 800 ° C.
It is also important to control the heating rate because the size and distribution of the precipitates change. That is, if the heating rate is slower than 5 ° C / s, coarse precipitation is likely to occur, and conversely if it is faster than 25 ° C / s, B
The precipitation amount of N becomes insufficient.

The cooling conditions after annealing are not particularly required, but the rapid cooling treatment increases the solid solution C in the steel to improve the primary recrystallization texture, and further, the rapid cooling treatment is combined with the rapid cooling treatment to obtain a low temperature. These treatments are effective when applied to the present invention, because the treatments for holding and precipitating fine carbide further improve the primary recrystallization texture. Further, decarburization of the steel sheet surface layer portion during annealing can obtain more preferable results.

Secondly, as an essential condition for effectively utilizing the method of precipitating fine BN in the temperature rising process of hot-rolled sheet annealing, BN is not precipitated as much as possible in the hot rolling step. If BN is precipitated in the hot rolling process, a large amount of BN already precipitated in the temperature rising process of hot-rolled sheet annealing is precipitated as precipitation nuclei, so that a small number of coarse precipitated BN are formed. Will be deteriorated.

In the hot rolling process, there are three points to prevent the precipitation of BN, and one of the points is to make the BN exist in the steel in a supersaturated solid solution state by setting the hot rolling end temperature to a high temperature. It is known that the precipitation temperature of BN changes depending on the Si content and the B content, so it is important to change the hot rolling end temperature in accordance with these contents. When the hot rolling finish temperature is low, BN is used in the hot rolling process.
Will be deposited. In the above experiment, the hot rolled sheet annealing was performed at a high temperature, and the hot rolled sheet annealing was performed at a low temperature.
In the product No. -1, a small number of coarse BNs are deposited, the suppressing force is reduced, and secondary recrystallization failure is caused, resulting in deterioration of magnetic properties.

Another point is that the steel sheet after the hot rolling is rapidly cooled. That is, this rapid cooling enables B to be frozen in the steel in a supersaturated state, and conversely, when the cooling rate is slow, BN tends to precipitate during the cooling process. The cooling rate required to prevent the precipitation of BN is 20 ° C./s or more.

The remaining one point is to lower the coil winding temperature after the hot rolling is completed, and since the coil is kept in the vicinity of the winding temperature for a long time, if the temperature is high, the BN also remains.
Will result in the precipitation of. In order to prevent the precipitation of BN, the coil winding temperature must be 670 ° C or lower.

Next, an experiment was conducted to investigate the proper range of the hot rolling finish temperature. Except that the Si content and the B content were intentionally changed, various slabs of 250 mm thickness for grain-oriented electrical steel sheets having almost the same composition as the above experiment were used, and the hot rolling end temperature was changed. Is the coil symbol A-1 in the above experiment
Each product was manufactured under the same conditions as above, and the value of the magnetic flux density B ₈ / B _s (B _s is the saturation magnetic flux density) of each obtained product was investigated.

FIG. 1 is a graph showing the influence of the Si and B contents of the material and the hot rolling finish temperature on the magnetic flux density B ₈ / B _s . From FIG. 1, the hot rolling finish temperature for obtaining a very high value of B ₈ / B _s of 0.95 or more is
(%) Is X and B (ppm) is Y
A value of X + 3Y or higher and a temperature of 950 ° C or higher is required,
Also, it can be seen that the temperature needs to be 900 + 35X + 3Y or less and 1150 ° C. or less. When the hot-rolling end temperature is lower than the above range, BN is mostly precipitated in the hot-rolling process, and when it is high, the BN is rolled in the high temperature region, and the width of the band structure of the hot-rolled sheet is increased. It is because it comes to interfere with the growth of recrystallization.

Thirdly, the crystal grain size of the secondary recrystallized grains is reduced by lowering the annealing temperature of the hot rolled sheet. The reason for this is not clear, but by lowering the annealing temperature, the amount of γ-transformation is decreased and the grain size before rolling is substantially increased, and the nucleation frequency of (110) grains in the rolling primary recrystallization structure is increased. It is presumed that this is due to an increase in.

It is a well known phenomenon that when the (110) grains increase in the primary recrystallized structure, the secondary recrystallized grains become finer. In this case, however, the magnetic flux density lowers than in the past. It was always the case. However, it is presumed that in the present invention, the effect of improving the magnetic flux density was obtained at the same time as the secondary recrystallized grains were made finer due to the strong inhibitory action of the inhibitor.

As for the cold rolling process, a one-time cold rolling method in which hot rolling sheet annealing is carried out and then one cold rolling is carried out, and a hot rolling sheet annealing is carried out and then the first cold rolling intermediate step is carried out. A second cold rolling method in which annealing is performed and then a second cold rolling is performed, or a hot rolled sheet annealing is omitted and a first cold rolling is performed followed by an intermediate annealing and then a second cold rolling. Any of the two-time cold rolling method of carrying out hot rolling can be adopted. In the first annealing (hot-rolled sheet annealing or intermediate annealing) performed in this cold rolling step, be careful to precipitate BN in the temperature rising process and prevent Ostwald growth, re-solid solution and re-precipitation of the precipitated BN. That is, Ostwald growth of BN precipitated even in the second annealing (intermediate annealing) in the case of performing hot-rolled sheet annealing and intermediate annealing,
It is important to pay attention to prevent re-dissolution / re-precipitation.

As for the cold rolling reduction rate, it is necessary to set the reduction rate of the final rolling to 80 to 95% as is conventionally known. When the rolling reduction of the final rolling is less than 80%, the crystal structure for growing the nuclei in the secondary recrystallized grains with an excellent orientation is insufficient, which causes a decrease in the magnetic flux density. Conversely, when it exceeds 95%, 2 The density of secondary recrystallization nuclei is reduced, and secondary recrystallization is apt to occur.

Experiment 2 As Experiment 2, investigation was carried out on the final finish annealing conditions. C: 0.08%, Si: 3.38%, Mn: 0.07%, Al: 0.008
%, Se: 0.020%, Sb: 0.035%, B: 0.0025% and N: 0.008%, the balance consisting essentially of Fe, and 10 slabs for grain-oriented electrical steel sheets with a thickness of 250 mm each at a temperature of 1420 ° C. After finishing the rough rolling to a plate thickness of 45 mm at a temperature of 1270 ° C and finishing rolling to a plate thickness of 2.2 mm at a temperature of 1020 ° C, spray a large amount of cooling water to 65 ° C / It was quenched at a cooling rate of s and wound into a coil at a temperature of 550 ° C.

These hot rolled sheets were heated at a heating rate of 9.5 ° C./s to anneal the hot rolled sheets at 1080 ° C. for 30 seconds, then pickled and then heated at 120 to 190 ° C. by a Sendzima rolling mill. Final cold-rolled sheet thickness: 0.30 mm was finished by warm rolling in the temperature range, degreasing treatment, decarburization and primary recrystallization annealing at 850 ° C. for 2 minutes, respectively.

Next, each of the decarburized annealed sheets was coated with the annealing separator shown in Table 2, and then the final finish annealing was performed up to a temperature of 1180 ° C. at a heating rate of 30 ° C./s. A heat pattern in which the temperature is decreased after being held for 400 hours
Up to the temperature of ℃, in the N ₂ atmosphere, after that, in the atmosphere shown in Table 2, respectively.

[0041]

[Table 2]

Then, after removing the unreacted annealing separator on each steel sheet, an insulating coating containing magnesium phosphate containing 50% of colloidal silica as a main component was applied, and the product was baked at a temperature of 800 ° C. did.

From each of the products thus obtained, an Epstein-size test piece having a long side in the rolling direction was cut out in the direction perpendicular to the rolling direction, subjected to strain relief annealing at a temperature of 800 ° C. for 3 hours, and then subjected to 1.7 T. Iron loss at magnetic flux density (
W _17/50 ) and magnetic flux density (B ₈ ) were measured, and the average crystal grain size of each product was also measured. The results of these measurements are summarized in Table 3.

[0044]

[Table 3]

As is clear from Table 3, the magnetic properties of the products of Condition Codes A and B, which had been subjected to the final finish annealing in a N ₂ simple atmosphere up to a high temperature, were deteriorated. Further, as components to be contained in the annealing separator, Ca, B and Ti
It can be understood that is a component advantageous for further improving the magnetic properties. This is due to the SiO ₂ formed on the surface of the steel sheet during decarburization annealing.
And MgO, which is the main component of the annealing separator, react at the time of final finish annealing to form a film containing forsterite (Mg ₂ SiO ₄ ) as the main component on the steel sheet surface.
It is considered that the addition of such components as Ti and Ti forms these nitrides or oxides in the film, enhances the strengthening action of the film, and increases the tension effect of the film, resulting in improved magnetic properties. To be

The atmosphere of the final finish annealing plays an important role in the formation of oxides and nitrides in the coating film, and by strengthening the reducibility particularly during the middle to the latter stages of annealing,
It is estimated that a better effect was obtained.

As a result of earnest research based on these experiments and investigations, the present invention has been completed.

Next, with respect to the component composition and the manufacturing method of the grain-oriented electrical steel sheet of the present invention, the requirements for obtaining the effects of the present invention, their range and action will be described in detail. First, the component composition will be described.

C: 0.025 to 0.095% If the content of C exceeds 0.095%, the amount of γ transformation becomes excessive, the distribution of Al during hot rolling becomes uneven, and the annealed hot-rolled sheet or the intermediate annealing is increased. The uniformity of the distribution of BN that precipitates in the temperature process is impaired, and the load of decarburization annealing increases, and decarburization failure easily occurs. On the other hand, if it is less than 0.025%, the effect of improving the structure cannot be obtained, and the secondary recrystallization becomes incomplete and the magnetic properties deteriorate. Therefore, its content should be in the range of 0.025 to 0.095%.

Si: 1.5 to 7.0% Si is an essential component for increasing electric resistance and reducing iron loss. For this purpose, it is necessary to contain 1.5% or more, but more than 7.0%. If it is contained as a component, the processability is deteriorated, and it becomes extremely difficult to manufacture the product or process the product. Therefore, its content should be in the range of 1.5 to 7.0%.

Mn: 0.03 to 2.5% Mn is an important component because it raises the electric resistance like Si and improves the hot workability during manufacturing. For this purpose, it is necessary to contain 0.03% or more, but 2.5
%, The magnetic properties are deteriorated by inducing .gamma.-transformation. Therefore, its content should be in the range of 0.03 to 2.5%.

In addition to these components, the steel requires an inhibitor for inducing secondary recrystallization, and it is necessary to contain B and N as inhibitor components.

B: 0.0008 to 0.0085% When the content of B is less than 0.0008%, the amount of BN precipitated during the temperature rising process of hot-rolled sheet annealing or intermediate annealing is insufficient, and good secondary recrystallization can be obtained. Can not. On the other hand, if it exceeds 0.0085%, the precipitation temperature of BN becomes high, and in normal hot rolling, B
The precipitation of N cannot be suppressed. Therefore,
Its content is in the range of 0.0008 to 0.0085%.

N: 0.0030 to 0.0100% When the content of N is less than 0.0030%, the amount of BN precipitated during the temperature rising process of hot-rolled sheet annealing or intermediate annealing is insufficient and good secondary recrystallization can be obtained. If it is not possible and conversely exceeds 0.0100%, it causes defects such as blisters in the steel. Therefore, the content is set to the range of 0.0030 to 0.0100%.

In addition to these components, some S
And / or Se must be included.

Sum of one or two of S and Se: 0.003 to 0.040% S and / or Se precipitate in steel as Mn compounds or Cu compounds, but most of them act as inhibitors. Instead, it functions as a precipitation nucleus of BN that precipitates in the temperature rising process of hot-rolled sheet annealing. Since a small amount of precipitates is sufficient for the nucleation of fine high-density dispersion, it is sufficient to contain 0.003% or more of each alone or in combination of both in order to exhibit this function. On the other hand, when it is contained in excess, it does not cause any harm because it only coarsely precipitates the excess, but when it is contained in excess of 0.040%, it precipitates at grain boundaries and hinders workability during hot rolling. . Therefore, the total content in the case of using each alone or in the case of the combination of both is within the range of 0.003 to 0.040%.

Further, Sb, Sn, Bi, Te, Ge, P, Pb, Zn,
Since In and Cr have an auxiliary function of strengthening the inhibitory force as inhibitors, it is preferable to add them to the steel at any time. The preferred content of each of these is in the range of 0.0010 to 0.30%. For other additive components, for example, N
Since i, Co, Mo, etc. have the effect of improving the surface properties of the steel sheet, they can be appropriately contained.

Next, the manufacturing method of the present invention will be described. The slab for grain-oriented electrical steel sheets adjusted to the above component composition can be manufactured by any conventionally known method.

The slab is subjected to normal slab heating and then hot-rolled to form a hot-rolled sheet coil. At this time, it is important that the slab heating temperature is 1350 ° C. or higher. one of. This slab heating temperature is 13
If the temperature is lower than 50 ° C., the solid solution of the inhibitor is insufficient, and a fine and uniform dispersed precipitation state of BN cannot be obtained in the subsequent annealing step. In hot rolling, known techniques such as thickness reduction treatment and width reduction treatment for uniformizing the structure before and after slab heating can be added at any time.

In this hot rolling, the four requirements listed below are essential. Firstly, the cumulative rolling reduction in finish rolling is set in the range of 85 to 99%. This is because when the rolling reduction is less than 85%, the band structure spacing in the hot-rolled sheet becomes large, which is harmful to secondary recrystallization, and conversely, when it exceeds 99%, recrystallized grains are present in the hot-rolled sheet. This is because the dispersed precipitation state of BN in the cold rolling step becomes rough.

Secondly, the finishing rolling temperature: T (° C) is 95
Temperature range from 0 ℃ to 1150 ℃, and Si (%):
Depending on X and B (ppm): Y, it is necessary to set the range to satisfy the following formula (1). 745 + 35X + 3Y ≦ T ≦ 900 + 35X + 3Y ---- (1) This is because if the finish rolling temperature is below the lower limit above, BN will precipitate during rolling, and BN will be finely uniform during hot-rolled sheet annealing and intermediate annealing. The desired magnetic characteristics cannot be obtained because no fine precipitate is obtained. On the other hand, if the upper limit is exceeded, rolling will be performed in a high temperature range, the density of defects in the steel will be reduced, and the precipitation of ultrafine sulfide or selenide, which becomes the nucleus of BN precipitation, will be suppressed, and This is because the uniform dispersion is hindered and the magnetic properties deteriorate.

Thirdly, it is necessary to quench rapidly at a cooling rate of 20 ° C./s or more after completion of hot rolling. That is, the quenching suppresses the precipitation of BN from the supersaturated state, and enhances the driving force for BN precipitation in the temperature rising process of hot-rolled sheet annealing or intermediate annealing.

Fourthly, the coil winding temperature is set to 670 ° C. or lower. This is because when the coiling temperature exceeds 670 ° C., BN from the supersaturated state is deposited, the inhibitory power of the inhibitor is deteriorated, and desired magnetic characteristics cannot be obtained.

In the cold rolling step, a single cold rolling method after hot rolled sheet annealing, a double cold rolling method in which intermediate annealing is sandwiched after hot rolled sheet annealing, or an intermediate annealing in which hot rolled sheet annealing is omitted is sandwiched. Two
Any of the cold rolling methods can be adopted. In the first annealing (hot-rolled sheet annealing or intermediate annealing) in this cold rolling step, fine precipitation of BN, which is the essence of the present invention, is performed in the temperature rising process, and the subsequent annealing step and the second annealing (intermediate annealing) are performed. It is extremely important to take care so as to prevent Ostwald ripening and re-solid solution / re-precipitation of the precipitated BN during annealing.

In the first annealing performed in this cold rolling step, that is, in the one-time cold rolling method and the two-time cold rolling method in which hot-rolled sheet annealing is performed, hot-rolled sheet annealing and hot-rolled sheet annealing are omitted. In the double cold rolling method, BN was used during the temperature rising process during the intermediate annealing.
In order to finely precipitate the
It is necessary to set the heating rate up to the temperature of 5 to 25 ° C./s. This is because when the temperature rising rate is less than 5 ° C / s, the precipitates are coarsely deposited, and a strong inhibitory force as an inhibitor cannot be obtained. On the contrary, when the heating rate exceeds 25 ° C / s, the amount of precipitates deposited is insufficient. This is also because the strong inhibitory power as an inhibitor cannot be obtained.

Further, it is necessary to carry out this annealing in the temperature range of 900 to 1150 ° C. for a holding time of 150 seconds or less.
That is, when the annealing temperature is excessively low, the strength of the (110) grains, which become nuclei for secondary recrystallization in the recrystallized structure after rolling, is insufficient, and the secondary recrystallized structure having a good orientation cannot be obtained. In order to obtain sufficient strength of (110) grains, it is necessary to coarsen the crystal structure after annealing to a certain size or more. For this purpose, it is essential to anneal at temperatures above 900 ° C. Also, regarding the upper limit of the annealing temperature,
The most important point is that BN finely precipitated in the temperature rising process should not be Ostwald-grown or re-dissolved.
To do this, set the annealing temperature below 1150 ° C and hold time
It is required to be 150 seconds or less. Thus, there is a feature of the present invention in lowering the annealing temperature, and thus it becomes possible to increase the strength of (110) grains in the structure of the primary recrystallized grains, resulting in high magnetic flux density and It is possible to obtain secondary recrystallization of a fine grain structure.

Regarding the cooling process of such annealing,
Although there is no particular point required, a quenching treatment to increase the solid solution C in the steel after annealing, a quenching treatment to precipitate fine carbide in the steel, and a subsequent low temperature holding treatment are performed. It is effective to improve the magnetic properties of the product. Here, the quenching process is a process of spraying a gas and / or a liquid as a cooling medium onto the steel sheet so that the cooling rate becomes faster than natural cooling, and for example, N ₂ gas is sprayed or mist water or jet water is sprayed. It is the process of cooling the sprayed steel sheet.

Further, known means for enhancing the oxidizing property of the annealing atmosphere to decarburize the surface portion of the steel sheet also effectively works. The decarburization amount in the hot-rolled sheet annealing before this final cold rolling and the intermediate annealing is
It is preferable to set it in the range of 0.005 to 0.025%. Such decarburization reduces the C content in the surface layer of the steel sheet and reduces the amount of γ-transformation during annealing, thus strengthening the inhibitory effect of the inhibitor in the surface layer portion of the plate thickness where nuclei of secondary recrystallization are generated. A preferable secondary recrystallization can be obtained. In order to obtain this effect, it is preferable to reduce the C content of the steel sheet by 0.005% or more. However, if it is reduced to more than 0.025%, the primary recrystallization structure is deteriorated, which is not preferable.

Regarding the second annealing (intermediate annealing) of the two-time cold rolling method after hot-rolled sheet annealing, the same as the first annealing for maintaining the state of finely precipitated BN and adjusting the crystal structure. Anneal for 150 seconds or less in the temperature range of 900 to 1150 ℃.

As for the reduction ratio of the cold rolling, it is necessary to set the reduction ratio of the final cold rolling within the range of 80 to 95%, as is conventionally known. This is because when the rolling reduction exceeds 95% secondary recrystallization becomes difficult, not the orientation of good secondary recrystallization grains is obtained is less than 80%, due to both the magnetic flux density of the product is degraded.

The first rolling reduction of the two-time cold rolling method is in the range of 15 to 60%. This is because if the reduction ratio is less than 15%, the rolling recrystallization mechanism does not work and the crystal structure cannot be homogenized. On the contrary, if it exceeds 60%, the crystal structure is integrated and the second rolling is performed. This is because the effect of will not be obtained.

Further, in the final cold rolling, as is well known, warm rolling in a temperature range of 90 to 350 ° C. is performed, and a pass in a temperature range of 100 to 300 ° C. for a time range of 10 to 60 minutes is performed. Performing the inter-aging treatment has the effect of improving the primary recrystallization texture, and more preferable results are obtained, so it is significant to apply it to the present invention.

After the final cold rolling, linear grooves may be provided on the surface of the steel sheet for subdividing the magnetic domains, as is well known.

The steel sheet having the final cold-rolled sheet thickness by such a method is subjected to primary recrystallization annealing by a known method, and then Mg
The annealing separator containing O 2 as a main component is applied to the surface of the steel sheet and then subjected to final finish annealing. Adding a Ti compound or adding Ca or B to the annealing separator further improves the magnetic properties. It is preferable because it has an effect.

In the final finish annealing, a small amount of heat
H from the temperature of 900 ℃ or more ₂Atmosphere containing
It is necessary to raise the temperature inside. That is, N up to high temperature
₂When annealed in an atmosphere, the steel sheet is
Nitriding progresses and the crystal grains with inferior orientation are secondary recrystallized and magnetic flux density is increased.
Cause deterioration of the degree. Therefore, the atmosphere of final finish annealing is
H at a temperature of at least 900 ℃₂Pass through
And are required. Also, H₂To create an atmosphere that includes
Is the content of Ti and Ca in the film, which is expected to improve the film tension.
And plays an important role in the formation of oxides and nitrides such as B
In order to do this, from the middle stage of annealing at a temperature of 900 ℃ or more
It is important to strengthen the reducibility especially in the second half
it is conceivable that.

After the final finish annealing, the unreacted annealing separator is removed, and then the surface of the steel sheet is coated with an insulating coating to obtain a product. However, if necessary, the surface of the steel sheet may be mirror-finished. However, the tension coating may be used as the insulating coating, and the coating and baking treatment of the coating may also serve as the flattening treatment.

Further, in order to reduce iron loss, the steel sheet after secondary recrystallization is subjected to linear plasma jet or laser irradiation as a known magnetic domain refining treatment, or linear dents are formed by a projection roll. It is also possible to carry out a treatment.

[0078]

【Example】

Example 1 C: 0.08%, Si: 3.32%, Mn: 0.07%, Al: 0.008%,
S: 0.003%, Sb: 0.02%, Se: 0.015%, B: 0.0035
% And N: 0.008%, with the balance being Fe and inevitable impurities, the slab is heated to a temperature of 1420 ° C and rolled to a sheet bar with a rolling finish temperature of 1230 ° C and a plate thickness of 45 mm. After that, after finishing rolling to finish rolling temperature: 1020 ℃ and plate thickness: 2.2mm, spray cooling water to 25 ℃.
It was cooled at a cooling rate of / s and wound into a coil at a temperature of 600 ° C. to obtain a hot rolled sheet coil.

This hot-rolled sheet was heated to 1100 ° C at 15.5 ° C / s.
The hot rolled sheet was annealed by raising the temperature at a heating rate of 30 ° C. and holding for 30 seconds, followed by pickling, and cold rolling to a sheet thickness of 1.5 mm. Next, this cold rolled sheet coil was divided into two equal parts and subjected to intermediate annealing in a H ₂ atmosphere with a dew point of 40 ° C. to reduce the C content to 0.06%.
At that time, one coil is 1080 ° C as a conforming example of the present invention.
・ 50 second annealing condition, the other coil is 1200 for comparison
The annealing conditions were 50 ° C. and 50 seconds. Each of these intermediate annealed sheets was finished by warm rolling at a steel sheet temperature of 220 ° C to a final cold-rolled sheet thickness of 0.22 mm.

Then, these cold rolled sheets were degreased and
After performing decarburization and primary recrystallization annealing at 0 ° C for 2 minutes,
After applying the annealing separator with 5% TiO ₂ added to MgO containing 5% Ca and 0.09% B, the final finishing annealing is performed in N ₂ atmosphere up to a temperature of 800 ° C at 30 ° C / h. From 800 ℃ in a mixed atmosphere of N ₂ : 25% and H ₂ : 75% at a heating rate of
The temperature is raised up to 1050 ° C at a temperature rising rate of 12.5 ° C / h, then in a H ₂ atmosphere up to 1200 ° C at a temperature rising rate of 25 ° C / h and kept at this temperature for 6 hours. After that, the temperature dropped.
At this time, H ₂ atmosphere up to a temperature of 600 ℃, N from 600 ℃
_Two treatments were performed to lower the temperature.

After the final finish annealing, the unreacted annealing separator was removed, and magnesium phosphate containing 50% colloidal silica was applied as a tension coating.
After baking at a temperature of 0 ° C., a plasma jet was irradiated at a pitch of 6 mm as a magnetic domain refining treatment to obtain respective products.

The measurement results of the magnetic characteristics investigated for these products are as follows. Magnetic density B ₈ (T) Iron loss W _17/50 (W / kg) Applicable example 1.964 0.678 Comparative example 1.902 0.938

As is clear from the above results, the comparative example of the present invention exhibits extremely excellent magnetic properties as compared with the comparative example in which the intermediate annealing temperature is outside the limited range of the present invention and is high.

Example 2 Each slab having various component compositions shown in Table 4 was
After heating to a temperature of 1430 ° C., after roughly rolling a sheet bar having a thickness of 50 mm at a temperature of 1250 ° C., the finish rolling end temperature is 1000 ° C. for the steels of symbols I to VII and X, symbol VIII,
1020 ℃ for XI, XII and XIV steels and 1100 ℃ for other steels, finish rolling to a plate thickness of 2.6 mm, jet water and cool at a cooling rate of 35-55 ℃ / s. The hot rolled sheet coil was wound into a coil at a temperature of 550 ° C.

[0085]

[Table 4]

These hot-rolled sheets were pickled, cold-rolled to a plate thickness of 1.8 mm, heated to 1080 ° C. at a heating rate of 15 ° C./s, and dew point: 50 ° C. for 50 seconds in an H ₂ atmosphere. After holding the intermediate annealing, the final cold-rolled sheet thickness was 0.26 mm by warm rolling at a steel sheet temperature of 230 ° C. After degreasing these cold-rolled sheets, decarburizing and primary recrystallization annealing at 850 ° C for 2 minutes, 8% TiO ₂ and 2% Sr (OH) ₂ were added to MgO. After applying an annealing separator and winding it into a coil, final finishing annealing is performed in an N ₂ atmosphere up to a temperature of 850 ° C at 30 ° C /
After raising the temperature at a temperature rising rate of h and holding at this temperature for 25 hours, the temperature is changed from 850 ° C to 15 ° C in a mixed atmosphere of N ₂ : 25% and H ₂ : 75%.
The temperature was raised to 1200 ° C. at a temperature rising rate of ° C./h, and the temperature was kept at this temperature for 5 hours in H ₂ atmosphere and then lowered.

After removing the unreacted annealing separator, a tension coating containing 60% colloidal silica was applied and baked to obtain a product. Table 5 summarizes the measurement results of the magnetic properties investigated for these products.

[0088]

[Table 5]

As is clear from Table 5, all of the conforming examples of the present invention show good magnetic characteristics as compared with the comparative examples in which the composition of the components is out of the limited range of the present invention.

Example 3 C: 0.075%, Si: 3.05%, Mn: 0.07%, Al: 0.012
%, S: 0.015%, Sb: 0.02%, B: 0.0010% and N: 0.0075% with the balance being Fe and unavoidable impurities. Slab (a), C: 0.078%, Si: 3.37
%, Mn: 0.07%, Al: 0.010%, S: 0.016%, Sb: 0.
A slab (b) containing 02%, B: 0.0038% and N: 0.0077%, the balance being Fe and inevitable impurities;
C: 0.068%, Si: 3.49%, Mn: 0.07%, Al: 0.011
%, S: 0.0016%, Sb: 0.02%, B: 0.0043% and N: 0.0075% with the balance being Fe and inevitable impurities, a slab (c) and C: 0.074%, Si: 3.
23%, Mn: 0.07%, Al: 0.009%, S: 0.004%, Sb:
A slab (d) having a composition containing 0.02%, B: 0.0022% and N: 0.0075%, with the balance being Fe and inevitable impurities.
2 pieces of each are heated to a temperature of 1390 ℃, and the plate thickness is 35mm.
Coarse rolling on the sheet bar of
And 2 types of 1055 ℃ and rolled to a thickness of 2.2 mm,
Jet water and quench at a cooling rate of 50 ° C / s to 57
The hot rolled sheet was wound into a coil at a temperature of 0 ° C.

Each of these hot-rolled sheets was annealed by heating the hot-rolled sheet at a temperature rising rate of 15 ° C./s to 1100 ° C. and holding it for 30 seconds, followed by pickling to an intermediate plate thickness of 1.5 mm. After cold rolling, intermediate annealing was performed. In this intermediate annealing, the temperature was kept at 1080 ℃ for 60 seconds, and then mist water was sprayed to 40 ℃ / s.
Carbide precipitation treatment was carried out by quenching at a cooling rate of 3 and holding at a temperature of 350 ° C for 30 seconds.

Thereafter, each steel sheet was subjected to an aging treatment between passes in a temperature range of 150 to 230 ° C. for 10 to 30 minutes by a Zenzimer rolling machine, and the final cold rolled sheet thickness: 0.22 mm.
Rolled into. After degreasing these cold-rolled sheets,
As a magnetic domain refinement treatment, grooves with a width of 50 μm and a depth of 20 μm were formed linearly at a pitch of 4 mm at an angle of 15 ° from the width direction of the steel sheet, followed by decarburization and primary recrystallization annealing at 850 ° C for 2 minutes. Giving,
7.5% of MgO containing 0.22% Ca and 0.08% B
After applying an annealing separator containing TiO ₂ and 3% SnO ₂ and winding it into a coil, the final finishing annealing is performed in N ₂ atmosphere at a temperature rising rate of 30 ° C / h up to a temperature of 850 ° C. After maintaining at this temperature for 25 hours, the temperature is raised to 1150 ° C in a mixed atmosphere of N ₂ : 25 and H ₂ : 75% at a heating rate of 15 ° C / h,
The temperature was maintained for 5 hours in an H ₂ atmosphere, and then the temperature was lowered.

After removing the unreacted annealing separator, a tension coating containing 50% colloidal silica was applied and baked to obtain respective products. Table 6 summarizes the measurement results of the magnetic properties investigated for these products.

[0094]

[Table 6]

As is apparent from Table 6, all the conforming examples of the present invention in which the hot finish rolling temperature (T) satisfies 745 + 35X + 3Y≤T≤900 + 35X + 3Y show extremely low iron loss.

Example 4 Five slabs having the composition of symbol VII in Table 4 above were heated to a temperature of 1400 ° C. respectively and rough-rolled to a sheet bar having a plate thickness of 50 mm, and finishing rolling temperature was 1030 ° C. , Thickness: 2.7m
After rolling to m, jet water at 40 ℃
It was rapidly cooled at a speed of / s and wound into a coil at a temperature of 600 ° C. to obtain hot-rolled sheets.

These hot-rolled sheets were heated at a heating rate of 17 ° C./s for 11
After hot-rolled sheet annealing is performed by raising the temperature to 00 ℃ and holding it for 60 seconds, pickling, cold rolling to final cold-rolled sheet thickness: 0.30mm, degreasing treatment, and 850 ℃ for 2 minutes Decarburization and primary recrystallization annealing were performed.

Thereafter, final finish annealing was carried out by applying the annealing separators A to E shown in Table 2 above and the annealing atmosphere conditions. As other conditions for this final finish annealing, the temperature was raised to 400 ° C. in an N ₂ atmosphere, the temperature was raised to 1200 ° C. at a heating rate of 25 ° C./s, and the temperature was kept at 1200 ° C. for 8 hours. Then the temperature dropped.

After the final finish annealing, after removing the unreacted annealing separating agent, aluminum phosphate containing 50% of colloidal silica was applied and baked at a temperature of 800 ° C. Then, a plasma jet was applied as a magnetic domain refining treatment. It was irradiated linearly at a pitch of 7 mm to make each product. Table 7 summarizes the measurement results of the magnetic properties investigated for these products.

[0100]

[Table 7]

As is apparent from Table 7, all the conforming examples of the present invention show extremely low iron loss.

[0102]

EFFECTS OF THE INVENTION The present invention uses a material whose component composition is limited and specifies hot rolling conditions, hot rolled sheet annealing conditions and intermediate annealing conditions to finely precipitate BN precipitation nuclei by pre-cold rolling annealing. According to the present invention, it is possible to manufacture a high magnetic flux density grain-oriented electrical steel sheet having an extremely low iron loss, which is advantageous for the recent demand for lower iron loss of iron core materials. Can handle.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of the Si and B contents of a material and the hot rolling finish temperature on the magnetic flux density B ₈ / B ₃ .

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-320766 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C21D 8/12 C22C 38/00 303 C22C 38 / 04 H01F 1/16

Claims (7)

(57) [Claims] 1. C: 0.025 to 0.095 wt%, Si: 1.5 to 7.
Contains 0 wt%, Mn: 0.03 to 2.5 wt% and one or two of S or Se: 0.003 to 0.040 wt%
And the balance being the material a steel slab comprising the composition of Fe and unavoidable impurities, the slab is heated to a temperature above 1350 ° C., after hot rolling, after subjected to hot rolled sheet annealing, between one cold after more final cold-rolled sheet thickness in <br/> rolling, subjected to primary recrystallization annealing to produce a grain-oriented electrical steel sheet by a series of steps of applying a final finish annealing after coating the subsequent annealing separator In this case, B: 0.0008 as an inhibitor component in the ingredient composition of the material
To 0.0085 wt% and N: 0.0030 to 0.0100 wt%, the finish rolling reduction of hot rolling is in the range of 85 to 99%, the finish rolling end temperature is in the range of 950 to 1150 ° C, and the material Si
From the relationship between the B content and the B content, hot rolling is performed within the range that satisfies the following formula (1), followed by rapid cooling at a cooling rate of 20 ° C / s or more and coiling at a temperature of 670 ° C or less. The temperature of the hot-rolled sheet annealing should be raised to a temperature of 800 ° C at a heating rate in the range of 5 to 25 ° C / s, and the holding time should be maintained in the temperature range of 900 to 1150 ° C.
Be carried out under conditions in which less 150 seconds, cold rolling, once reduction ratio by cold rolling: To a final cold-rolled sheet thickness is performed at 80% to 95% range, the final annealing temperature increase in the middle A method for producing a high magnetic flux density grain-oriented electrical steel sheet having extremely low iron loss, which is sequentially combined with heating in an atmosphere containing H ₂ from a temperature of at least 900 ° C or higher. [Note] 745 + 35X + 3Y ≦ T ≦ 900 + 35X + 3Y --- (1) However, T: Finishing rolling end temperature (° C) X: Si (wt%) Y: B (wtppm) 2. C: 0.025 to 0.095 wt%, Si: 1.5 to 7.
0 wt%, Mn: 0.03 to 2.5 wt% and S or Se
1 or 2 in total: 0.003 to 0.040 wt%
However, the balance is steel slurry with a composition of Fe and unavoidable impurities.
Using slab as a material, heat the slab to a temperature of 1350 ° C or higher
After hot rolling, hot-rolled sheet annealing is performed, and then intermediate annealing is performed.
The final cold-rolled sheet thickness is set by sandwiching two cold rolling steps, then 1
Subsequent recrystallization annealing is applied, and then the annealing separator is applied.
Grain-oriented electrical steel sheet by a series of processes for final finishing annealing
In the production of B, as an inhibitor component, B: 0.0008
Up to 0.0085 wt% and N: 0.0030 to 0.0100 wt%
Rukoto, a finish rolling reduction ratio of hot rolling in the range 85 to 99% Specification
The finish rolling temperature is in the range of 950 to 1150 ℃ and the material Si
Range satisfying the following formula (1) from the relationship between the content and the B content
After performing hot rolling, the cooling rate should be 20 ℃ / s or more.
Rapid cooling and coiling at a temperature of 670 ° C or less, both hot-rolled sheet annealing and intermediate annealing to a temperature of 800 ° C
The temperature is raised at a heating rate in the range of 5 to 25 ° C / s,
Do this under the condition that the holding time is 150 seconds or less within the temperature range.
And, in the cold rolling, the rolling reduction of the first rolling: 15-60%
The second rolling after the intermediate annealing.
Ratio: 80-95% of the final cold-rolled sheet thickness , at least 900 ° C or higher during the final finishing annealing
The order of increasing the temperature in an atmosphere containing H ₂
High magnetism with extremely low iron loss characterized by the following combination
A method of manufacturing a bundle density grain-oriented electrical steel sheet. [Note] 745 + 35X + 3Y ≦ T ≦ 900 + 35X + 3Y --- (1) However, T: Finish rolling end temperature (℃) X: Si (wt%) Y: B (wtppm) 3. C: 0.025 to 0.095 wt%, Si: 1.5 to 7.
0 wt%, Mn: 0.03 to 2.5 wt% and S or Se
1 or 2 in total: 0.003 to 0.040 wt%
However, the balance is steel slurry with a composition of Fe and unavoidable impurities.
Using slab as a material, heat the slab to a temperature of 1350 ° C or higher
Then, after hot rolling, two cold rolling steps with intermediate annealing
After the final cold-rolled sheet thickness is obtained, primary recrystallization annealing is performed,
A sequence of applying post-annealing separator and then final finishing annealing
In the production of grain-oriented electrical steel sheet by the process of B, 0.0008
Up to 0.0085 wt% and N: 0.0030 to 0.0100 wt%
Rukoto, a finish rolling reduction ratio of hot rolling in the range 85 to 99% Specification
The finish rolling temperature is in the range of 950 to 1150 ℃ and the material Si
Range satisfying the following formula (1) from the relationship between the content and the B content
After performing hot rolling, the cooling rate should be 20 ℃ / s or more.
Rapid cooling and coiling at a temperature of 670 ° C or less, intermediate annealing, heating up to a temperature of 800 ° C in the range of 5 to 25 ° C / s
The temperature is raised at a speed and the holding time is 1 in the temperature range of 900 to 1150 ° C.
It is performed under the condition of 50 seconds or less, and in the cold rolling, the first rolling is a reduction rate: 15 to 60%
The second rolling after the intermediate annealing.
Ratio: 80-95% of the final cold-rolled sheet thickness , at least 900 ° C or higher during the final finishing annealing
The order of increasing the temperature in an atmosphere containing H ₂
High magnetism with extremely low iron loss characterized by the following combination
A method of manufacturing a bundle density grain-oriented electrical steel sheet. [Note] 745 + 35X + 3Y ≦ T ≦ 900 + 35X + 3Y --- (1) However, T: Finish rolling end temperature (℃) X: Si (wt%) Y: B (wtppm) 4. The steel slab further comprises Sb, Sn, Bi, Te,
One selected from Ge, P, Pb, Zn, In and Cr
It is contained in a range of two or more of each 0.0010～0.30Wt% is
4. The composition according to claim 1, wherein the composition is
Of high magnetic flux density grain-oriented electrical steel sheet with extremely low iron loss
Production method. 5. The cooling in the final cold hot-rolled sheet annealing immediately before rolling or intermediate annealing, high low very iron loss of any one of claims 1 to 4, cooling rate than natural cooling Flux density grain-oriented electrical steel sheet manufacturing method. 6. The extremely low iron loss according to any one of claims 1 to 5 , wherein 0.005 to 0.025 wt% of decarburization is performed by hot-rolled sheet annealing or intermediate annealing immediately before final cold rolling. Manufacturing method of low magnetic flux density grain-oriented electrical steel sheet. 7. The final cold rolling is either warm rolling in the temperature range of 90 to 350 ° C. or 10 in the temperature range of 100 to 300 ° C.
The method for producing a high magnetic flux density grain-oriented electrical steel sheet with extremely low iron loss according to any one of claims 1 to 6, wherein the inter-pass aging treatment is performed for a time range of -60 minutes.